Keeping BBBs "trim"?

Hi there, we have two BBB hens that are probably a little over a year old. We got them simply to be pets, (and for us to eat the eggs, of which they have just now started to lay a few). They free range over a very large enclosure and we toss them standard poultry feed morning and night, but I am wondering if I should replace a poultry feeding with more fruit and vegetable scraps? Give them only a couple handfuls of store bought feed a day? Or is that not enough? I take the pulp from our juicer out there and toss the vegetable pulp out to them, and they just look at me and gobble and wait for something else...but when I walk away they will usually grudgingly peck at it.

Anything else I should do regarding diet management if I want them to stick around awhile (I know they are genetically engineered to just get fat quick and fall over...)